Dipole Impedance

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P.S my dipole is precisely 50 OHM and so is the coaxial cable so no need for impedance transformation. I only need to eliminate the coax shield currents.
How did you achieve that ? ... dipoles are 75 Ohms by nature ( folded ones 300 Ohms) ... what impedance matching did you do ?
Dave

A DNA dipole is a charge voltage and as such the load impedance must be extremely high on the amplifier so as not to discharge the dipole as well as low capacitance relative to the sensor electrodes and medium.
A suitable choice would be any good low noise JFET Preamplifier design.
is one.

Hi
I have a question about the Radiation Boundary in HFSS itself. I am simulating a dipole with a lumped port feed and I notice changes in the resonant impedance/frequency when I change the size of the Radiation Boundary. According to the design requirements, I gathered that the minimum distance of the radiation boundary away from the radiating

1/2 lambda length of the coaxial cable balun act as 4:1 for impedance, and 2:1 for voltage.
3/2 lambda may work, but you don't get 4:1 impedance ratio anymore.
At 2.4 GHz I would recommend do not use a folded dipole for the driven element, because anyway the bandwidth of a standard 1/2 lambda dipole (~73 ohms) at that (...)

I have tried to simulate a half wave dipole with HFSS using PEC. The dipole is 38.75mm long with a small gap (0.4mm) between the two arms to allow a lumped port to be put there. So this should be a half wave at around 1.8GHz.
But the imaginary impedance does not even reach 0 (smaller than 0). How can I determine the input resistance of (...)

Hi
in literature sometimes we give the input impedance as a function of L / lambda0 (normalized length)
Please, can someone show me how to do to plot it as a function of L / lambda in HFSS for whatever structure (e.g. for a dipole, or a patch antenna). of course I know how to do it as a function of frequency.
Thanks

Not quite. That is contradictory.
For a dipole you can choose 1/4, 1/2 and 1 wavelength. Resonance is non reactive just below theoretical due to fringing and thickness.
more details here 1/2 wave is most common.

hi guys..
what happens to the feed resistance of an antenna when the reflector and the director are placed on either side of a dipole?
it generally lowers the feedpoint impedance
what happens to the beamwidth when the number of directors are increased?
it narrows
what is the app

You can get a formula for the complex impedance of the antenna from Wikipedia under "Short dipole" on the "dipole Antenna" entry. and there is a section on "General impedance can use a calculator on it. You will be looking to

how to design a co planar stripeline feed and integrate it to dipole antenna with reflector?. i have designed the antenna but it is showing a VSWR of 3 instead of 2 . need assistance for design and integration. impedance is 150 ohm and hence need to design the width of the feed and gap of the feed to the dipole antenna ant to integrate.

One-tenth wavelength dipole, 1.9 GHz on FR4 PCB. About 10 mm long antenna?
Yes it is possible to design and impedance match a such antenna.
Anyone can do it. Very few can do it and get reasonable performance. Good skills how to set up a VNA is recommended as short antennas and extreme impedances both requires good calibration to be able to (...)

Clarification of terms.
you say "dipoles are λ/2". At which frequency?
How do you measure "mutial impedance" of antennas? In network analysis, mutual impedance involves a driving current source and open circuit voltage measurement, which is hard to implement in RF frequency range.

You are correct, your formula for gamma is only valid for Im(Zin) = 0 (that is Xin=0). You can see that when plotting the impedance on a Smith Chart. When there is an Im(Zin) part, the impedance moves towards the edge of the Smith Chart.
Can it be that the length of the antenna is specified as the length of one half of the dipole? So (...)

Hello,
I have simulated a dipole antenna at HFSS. Now, I would like to use it in a design at ADS. In this way, I would like to have a two-port block that would mimic the impedance frequency dependency of the antenna. Probably at port 1, the impedance should be always equal to 50ohms, while the impedance at port 2 should (...)

Hello,
I'm trying to make a dipole antenna for UHF (433 MHz). I have a 50 Ohm unbalanced output so I need to balance it and do an impedance matching to get the best performance possible. I bought some Minicircuits' ADT1.5-1 ( ) to do the job.
I made a PCB, soldered the transformer and the legs of th

Hi there,
I am working on printed dipole antenna array.
I an new for XFDTD design, and I really need help.
For making understanding, I started to design Microstrip ; one end I put feed component 50 ohms
and put passive load 50 ohms on the other end. The result was as I expected.
After that, I designed a patch antenna at 2.4 GHz and i

Hi, I'm pretty new to FEKO but as an assignment, our professor wants us to create a dipole and analyze it "over a broad spectrum" On his sample graphs he showed us a plot of the impedance vs dipole Length. I was wondering how to do this. I can create a dipole using a fixed length but I can't seem to figure out if it's (...)

Is your bow antenna above a ground plane, as this has large influence on input impedance?
feeding a dipole off-center, will raise the impedance, but you get a large common mode component, that will increase the common mode current in the coaxial feed line. The common mode current contributes to the radiation pattern (mostly not desired). (...)

Dear all,
I have a question about matching a printed folded dipole.
I am working at 2.45GHz
My antenna is connected to a 50 ohms /50 ohms balun, then connected to a 2-ports VNA, for s11 evaluation.
At the frequency of interest, the impedance is Z; is this the impedance of the antenna seen from the VNA?
Because I need to tune this (...)

I believe the HFSS Antenna Design Kit (ADK) can be extended by adding your own code, but does anyone have any instructions on how to do this? For example, lets assume I want to be able to design a folded dipole to have a specific impedance. One can achieve this by having the two sides of the dipole of a different diameter, and there are (...)

I have 5-element λ/2 dipoles spaced 0.1λ apart (they all show in the model...I am not using the Antenna Array Setup wizard). They are all excited with 1W each and the port impedance for each is 73ohms. After simulation, the power accepted is about half less than power incident. When simulating one half-wave dipole alone with 73ohms (...)

Hi everyone
I want to use HFSS to design dipole phased array antenna. is there anyway to use Tschebyscheff coefficients for amplitude?
in hfss----radiation----array design menu there is not any option to choose amplitude coefficient. would u please help me?

dipole of the same physical length immersed in water.
Actually, what Deborah and myself have analyzed was a dipole embedded in a dielectric tube of finite size (smaller than the wavelength in air), surrounded by air.
What I did not yet understand is the physical setup that Deborah wants to simulate, i.e. if the an

Hi alberthyc,
Could you share how you figured out where the remaining power went? I'm trying to impedance match a 5-element dipole array but with no luck. I tried to match it with Active Z re and im values, but I still get power accepted much less than power incident.
Thanks.

I am trying to impedance match a 5-element dipole array in HFSS using the Active Z re and im values, but I am not getting good S11 with it. How do you achieve good impedance matching of array elements?
Please help all you HFSS experts out there.

How does one obtain the active input impedance of a 5-element dipole phased array in HFSS?
I am using the Active Z measurement and plot re and im values. Is this correct?
When I do this I get different impedance values for each of the elements. Shouldn't the impedance values be symmetrical around the center array, for (...)

Anybody in work on UHF RFID design?
We've been discussing differential impedance measurement for RFID antennas or tag chips, one question still bothers me, which is below.
As we all know,dipole has differential ports, as the load of antenna,the TAG CHIP usually has single-ended port. Such as NXP/Alien, the tag chips have only one RF port and

Hi,
I am currently designing 433MHz half wave Printed dipole Antenna with input impedance of 50 ohm using Ansoft HFSS 13. The problem is, i can't seem to figure out how to efficiently place the ground plane in the design. This is because, either the simulated radiation pattern is severely distorted or my Z11 graph and smith chart is does not yiel

If you have extended DUT ground plane with a measurement cable can this type of problem occur. Please check the section about how to reduce measurement cable related S11 problems.
For S11 measurement is normally not any chamber needed.
Thanks to your advice. y

Folded dipoles with equal diameter wires in both parallel lines increase the impedance by 4x. This will increase the lowered impedance (caused by the parasitic elements) to be more nearly equal to 50 ohms and make the impedance matching to the coax easier.

Hello all
I am trying to design a dipole antenna using HFSS. In my design i plotted a graph for input impedance Vs frequency and it seems that instead of somewhere close to 73 ohms i am getting it to 117 ohms which is way to can anybody take a look and tell me what is wrong with a design and how can i get a output close to 73 ohms?or th

Hello everybody,
I'm trying to simulate a dipole with a voltage source in the middle of them. For that, I'm using a lumped port that is found in the middle of the dipoles, and it have the voltage that I want. But i'm having a very small input impedance. An I doing something wrong?
I found to a model tutorial simulate that use the lumped (...)

I've tried to simulate a half-wave dipole in HFSS, using a perfect electrical conductor (pec). The dipole is 500 mm long in total, with a small gap between the two arms to allow a lumped port to be put there. So this should be a half-wave at 300 MHz.
Using a wire radius of 1 mm, with a 1 mm gap between the terminals, the input impedance (...)

A quarterwave "whip" monopole will have an input impedance of Zin = 36.5 + j21.25 ohms at it's resonant frequency. A half-wave dipole would be 70 ohms. You can replace your antenna with one of these two loads, depending on what type of antenna you intend to drive. It should work as a first-order approximation.

I want to read on input and characteristic impedance on a simple dipole and all the basic theoretical material concerning the calculation and understanding the concept can any body recommend a certain place which will give that information
many thanks

One lambda in air is 190mm, so an electrically straight half wave dipole will be in the range of your 89mm (because of influence of dielectric and fringe capacitance at the dipole ends). Your resonance has low impedance when you feed the antenna about in the middle.
A full wave antenna (fed in the middle) will have high (...)

Need Guidance
OK i have a dipole whose Zi changes due to close proximity of parasitic elements.
Complex input impedance is 150+160i .
And its surely complex (not 200 ohm ) due to parasitic effects :)
How can i achieve it practically.
Can Quarter Wave transformer be used in this case. if it can how can i use it somehow with a balun. I m usin

Hello all
If I am plotting a graph for Input impedance vs frequency graph for dipole antenna using HFSS version 11. than how can i check that plot is correct or not?i mean my design is accurate or not?
One thing that i know is as following:
When the imaginary part of input impedance crosses 0 at that time the real value (...)

Hello All,
In an attachment to this message, dipole antenna model is attached.
can any body have suggestions, how to improve s21, s12 parameters without changing distance between dipole antenna.impedance matching is almost perfect.

Hi, I want to design a magnetic dipole to use for frequency 2,45 GHz. My results are
Wavelength: λ=300 / 2450 MHz = 0.122 m
Diameter of the loop:
0,122 m/ 3,14 =0,0388 m =3,885 cm. Now I'd need to know the impedance of this antenna, but cant find out how to calculate it. The ideal impedance would be cca. 75 ohm. Should I divide (...)

hi, i designed UHF rfid tag antenna (860Mhz-960Mhz) which is a meandered half wave dipole antenna on FR4. As it needs balanced signal at its input to measure the input impedance etc. of this antenna. VNA provides unbalanced signal. I am confuse how do I make a balun or any measuring structure with which I can provide balanced signal to it.
Anybody